Your choices:
1 Electricity; 2 Comfortable indoor climate; 3 Water
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| Biomass (digestible sludge) | District cooling | 2 Comfortable indoor climate |
| Biomass (fermentable sludge) | District heating | Electricity |
| Biomass (solid) | 1 Electricity | Process cooling (< 0 °C) |
| Geothermal | Fuel: Gaseous | Process heat/steam (50 - 150 °C) |
| Sunshine | Fuel: Liquid | Process heat (150 - 1000 °C) |
| 3 Water | Fuel: Solid | Process heat (> 1000 °C) |
| Wind | Local cooling (ind. house) | Transport |
| Residual oils/fats etc | Local heating (ind. house) |
Electricity is the king of energy carriers and should not be used for low-exergy purposes such as indoor climate control.
In case the electricity is produced in a hydroelectric power station, and this is by far the best way to produce electricity, then will the output from the power station always exceed the needs of an individual building. Even a 10 kW generator, running only 8 h/day 200 days per year as may be the case in the smallest imaginable micro-installation will produce 16000 kWh per year which is enough for a normal single-family household.
Therefore, hydroelectricity is not to be seen as a produce for the individual household but should always be regarded as a commercial product traded and exchanged via the general electricity grid. And then, the general thermodynamic constraints apply and it should generally not be used for low-exergy services but should be contracted to provide such services for which the unique features of electricity are appreciated.